Flexible tracked vehicles are generally well known in the art, and are well-suited for many applications in which more conventional wheeled vehicles are unsatisfactory. For example, conventional wheeled vehicles traditionally do not have enough traction to operate in and around most construction sites, and thus a tracked vehicle, which spreads its load over a much greater area, is much more capable of traversing the rough and often muddy terrain at such construction sites. Bulldozers and certain types of paving machines are two examples of commonly used flexible tracked vehicles.
Most heavy tracked vehicles, such as bulldozers, use a flexible metal belt made go of a plurality of connected links, and are driven by a positive drive system in which a drive wheel engages teeth or cogs on the inside of the metal belt. On the other hand, many lighter duty flexible tracked vehicles use a flexible continuous rubber track incorporating a friction drive system. In contrast to a positive drive system, a friction drive system relies on the friction between the drive wheel and the track or belt in order to transmit motive force to the belt and hence the ground. The flexible track extends between a drive wheel and a free wheel, and an idler assembly is used to apply pressure to the free wheel in order to maintain the proper tension on the drive belt. The free wheel is slidably or adjustably mounted in a carriage assembly, and a compression spring or a gas charged cylinder applies outward force to the carriage assembly, thereby applying tension to the belt.
On friction drive systems, proper belt tension is critical to the operation of the vehicle. Unfortunately, when the drive system of the vehicle is reversed, the force applied against the free wheel, and hence the idler assembly, increases significantly. In such a state, a much greater force is required in order to maintain the proper belt tension. If not enough force is applied to the idler assembly and the belt tension decreases significantly, the carriage assembly and the free wheel will be drawn toward the drive wheel, and the belt will begin to bunch and/or slip. In some instances, the belt may even become untracked.
Consequently, the typical approach is to maintain a high level of force against the carriage assembly at all times. Unfortunately, this approach significantly increases the load on the drive components of the vehicle during normal forward operation. Many system components are thus subjected to increased wear and tear, which leads to premature system failure. Accordingly, there exists a need for an improved tensioning device or idler assembly that will automatically adjust to different operating conditions in order to prolong the life of the drive system and its components.